Gasoline composition

ABSTRACT

This invention relates to a fuel composition comprising (i) a low sulphur fuel having a sulphur content of less than 30 ppm, a bromine number of less than 10 and an ultraviolet absorbance at 319 nm is below 0.15 and (ii) an effective amount of an ashless friction reducing additive which is a fatty acid having 10-30 carbon atoms or a derivative thereof. The fuel of the specified characteristics shown improved response to the friction reducing additive in respect of its lubricity performance.

[0001] This invention relates to low sulphur gasoline compositions whichhave improved response to friction reducing additives.

[0002] Fuels such as gasolines and diesels are used rather widely inautomotive transport and for providing power for heavy duty equipment,especially diesels due to their high fuel economy. However, one of theproblems when such fuels are burned in internal combustion engines istheir low lubricity. This reduction in lubricity arises because as thesulphur content in the fuel is reduced eg by hydrodesulphurisation, thisprocess also incidentally removes the lubricity providing polar orfriction reducing molecules such as eg the nitrogenous compounds presentin such fuels. A prior published SAE Paper No. 962010 by Wei Dan Ping etal entitled “Comparison of the Lubricity of Gasoline and Diesel Fuels”(1996) describes the effects of various additives on such fuelsincluding low sulphur fuels. Whilst efforts hitherto have been devotedto the addition of such friction reducing nitrogenous compounds into thefuels after hydrodesulphurisation to restore the lubricity of the fuel,little attention has been paid to the nature of the fuel itself in orderto improve the efficiency of such fuels.

[0003] Prior published GB-A-2306246 and GB-A-2307247 relate to the useof carboxylic acid derivatives as an additive for improving thelubricity of low sulphur-content fuels which are primarily middledistillate fuels such as eg diesel, jet and biodiesel fuels. However,there is no mention of gasolines or fuels having a sulphur content ofless than 30 ppm in these documents.

[0004] Similarly, EP-A-0860494, EP-A-0739970 and EP-A-0635558 relate tolow sulphur diesel, gas oils and gas oils (diesel fuels) respectivelycontaining esters derived by transesterification of vegetable oils,glycerol/fatty acid esters and lower alkyl esters of a mixture ofsaturated and unsaturated fatty acids derived from oleaginous seedsrespectively as a lubricity improving agent. In each case there is nomention of low sulphur gasolines, especially gasolines having a sulphurcontent of <30 ppm.

[0005] WO99/00467 describes a fuel composition of improved lubricitycomprising a spark ignition fuel and an alkanolamide of a fatty acid ora modified fatty acid having a maximum sulphur content of 0.05% based onmass. However, no gasolines are mentioned and all of the examples relateto diesels, especially Swedish Class I low sulphur diesel fuel. There isalso no reference to the bromine number or UV absorbance of the fuelstested or claimed.

[0006] It has now been found that the efficacy of the friction reducingadditives can be significantly improved by mixing the same with fuels ofspecific, predetermined characteristics.

[0007] Accordingly, the present invention is a composition comprising(i) a low sulphur gasoline having a sulphur content of less than 30 ppm,a bromine number of less than about 10 and an ultraviolet absorbance at319 nm below 0.15 and (ii) an effective amount of an ashless frictionreducing additive which is a fatty acid having 10-30 carbon atoms or aderivative thereof.

[0008] The gasoline should have a bromine number (which is related tothe amount of olefins in the fuel) below 10, suitably below 5 andpreferably below 4.5. Furthermore, the gasoline should have a sulphurcontent below 30 ppm, suitably below 20 ppm and preferably below 10 ppm.Again the UV absorbance of the fuel at 319 nm should be below 0.1,suitably below 0.07 and preferably below 0.05.

[0009] The ashless friction reducing additive in the composition issuitably a liquid at room temperature and pressure and is selected fromC10-C30 fatty acids, preferably a C10-C24 fatty acid, or a derivativethereof and mixtures thereof. Such ashless friction reducing additivesare suitably derived from naturally occurring fats and oils and thepreferred derivatives are suitably selected from the alkylamine salts,alkyl amides and alkyl esters of such acids and oligomers thereof. Anexample of an alkyl amine carboxylate salt is n-butylamine oleate or aderivative thereof and an example of a naturally occurring fatty acid isa substance comprising a fatty acid, a tall oil fatty acid orderivatives thereof.

[0010] n-Butylamine oleate has the formula:

CH₃—(CH₂)₇—CH:CH—(CH₂)₇—C(O)O⁻⁺NH₃C₄H₉

[0011] One such n-butylamine oleate is commercially sold as a frictionmodifier as RS124 by Bitrez Ltd.

[0012] The substance comprising fatty acids may be either 100% fattyacids, or substantially 100% fatty acids, or may be a mixture of fattyacids and/or tall oil acids or derivatives thereof. Such a mixturesuitably contains at least 30% w/w, preferably at least 50% w/w of fattyacids. An example of a suitable commercially available substancecontaining fatty acids is TOLAD® 9103 (ex Baker-Petrolite Ltd).

[0013] The friction reducing additive is used in an amount sufficient toprovide effective lubricity to the composition. The friction reducingadditive is suitably used in an amount of less than 1000 mg per kilogramof base fuel in the composition, preferably from 1 to 500 mg and morepreferably from about 5 to 100 mg per kg of base fuel in thecomposition. It has been found that a gasoline with thesecharacteristics is much more responsive to the amount of the ashlessfriction reducing agent specified above added than conventional fuelswhich do not possess these characteristics. A typical example of such agasoline is the so called “Rotterdam gasoline” which suitably has afinal boiling point below 200° C., preferably about 185° C. The ashlessfriction reducing additive may be part of an additive concentratecomprising a number of additives. In the additive concentrate, theamount of the friction reducing additive is suitably from 0.2-25% w/w,preferably from 0.5-20% w/w and more preferably from 3 to 15% w/w. Onthe basis of the total concentrate, the treat level of the frictionreducing additive in the gasoline is suitably from 4-200 ppm, preferablyfrom 10-100 ppm and more preferably from 25-75 ppm.

[0014] The present invention is further illustrated with reference tothe following Examples and comparative tests:

EXAMPLES

[0015] The following fuels with varying degrees of bromine numbers,sulphur content and UV absorbance at 319 nm were tested for theirresponsiveness to a lubricity additive. Of these, both the Rotterdam andthe Neste 95UL base gasolines show comparable sulphur contents, yet theRotterdam fuel (which has a final boiling point of 186.2° C.) is moreresponsive to lubricity additive. This responsiveness, as measured bythe percentage reduction in friction relative to base fuel (Table 2) islinked to the fuel's substantially lower bromine number and UVabsorption at 319 nm. (Table 1) (Note: the measure of UV absorbance andbromine number are both dimensionless quantities). TABLE 1 FUEL & SOURCEBROMINE NO. % SULPHUR BY WT UVA (319 nm) Fawley (A)* 37.72 0.04 0.398Neste 95UL* 21.7 0.0027 0.323 Rotterdam 4.17 0.0028 0.038 Fawley (B)*16.11 0.01 0.172 Fawley (C)* 13.28 0.02 0.567

[0016] The above fuels were tested at various treat rates to determinethe change in coefficient of friction and the mean friction values andthe results are tabulated in Tables 2 and 3 below: TABLE 2 Treat RateBase Fuel Additive ml/1000 litres Mean FC ΔFC % ΔFC Fawley (A) None 00.224 Fawley (B) n-BAO 12.5 0.154 0.071 31.5 Fawley (C) Tolad ® 910312.5 0.145 0.079 35.3 Neste 95 UL None 0 0.225 Neste 95 UL n-BAO 12.50.152 0.073 32.5 Neste 95 UL Tolad ® 9103 12.5 0.153 0.072 32.1Rotterdam# None 0 0.439 Rotterdam# n-BAO 12.5 0.157 0.283 64.4Rotterdam# Tolad ® 9103 12.5 0.152 0.287 65.5 Fawley (B) None 0 0.304Fawley (B) n-BAO 12.5 0.158 0.146 47.9 Fawley (B) Tolad ® 9103 12.50.214 0.090 29.7 Fawley (C) None 0* 0.315 Fawley (C) n-BAO 12.5* 0.2040.111 35.2 Fawley (C) Tolad ® 9103 12.5* 0.218 0.097 30.8

[0017] TABLE 3 Treat Rate Mean Friction % ΔFriction Base Fuel Additivemg/Kg Coefficient Coefficient Fawley (C) None 0 0.315 Fawley (C) n-BAO12.5 0.204 35.2 Fawley (C) n-BAO 25 0.146 53.6 Fawley (C) n-BAO 50 0.13258.1 Fawley (C) n-BAO 100 0.118 62.5 Fawley (C) None 0 0.315 Fawley (C)Tolad ® 9103 12.5 0.218 30.8 Fawley (C) Tolad ® 9103 25 0.174 44.8Fawley (C) Tolad ® 9103 50 0.149 52.7 Fawley (C) Tolad ® 9103 100 0.13756.5

1. A composition comprising (i) a low sulphur gasoline having a sulphurcontent of less than 30 ppm, a bromine number of less than 10 and anultraviolet absorbance at 319 nm below 0.15 and (ii) less than 1000 mgper kg of the low sulphur gasoline of an ashless friction reducingadditive which is a fatty acid having 10-30 carbon atoms or a derivativethereof selected from the alkylamine salts, alkylamides and alkylestersof such acids and oligomers thereof.
 2. A composition according to claim1 wherein the gasoline has a bromine number below 5 ppm.
 3. Acomposition according to any one of the preceding claims wherein thegasoline has a sulphur content below 20 ppm.
 4. A composition accordingto any one of the preceding claims wherein the gasoline has an UVabsorbance at 319 nm of below 0.07.
 5. A composition according to anyone of the preceding claims wherein the fatty acid is derived fromnaturally occurring fats and oils and oligomers thereof.
 6. Acomposition according to any one of the preceding claims wherein theashless friction reducing additive is an alkylamine salts of a fattyacid derived from naturally occurring fats and oils and oligomersthereof.
 7. A composition according to any one of claims 1-4 wherein theashless friction reducing additive is an alkylamide of a fatty acidderived from naturally occurring fats and oils and oligomers thereof. 8.A composition according to any one of the preceding claims 1-4 whereinthe ashless friction reducing additive is an alkylester of a fatty acidderived from naturally occurring fats and oils and oligomers thereof. 9.A composition according to claim 6 wherein the alkylamine carboxylatesalt is n-butylamine oleate as shown in the formula below or aderivative thereof CH₃—(CH₂)₇—CH:CH—(CH₂)₇—C(O)O⁻⁺NH₃C₄H₉
 10. Acomposition according to any one of claims 1-4 wherein the long chainfatty acid or a derivative thereof is a substance comprising tall oilacid or derivatives thereof.
 11. A composition according to claim 10wherein the substance containing fatty acid is TOLAD® 9103 (ex PetroliteLtd).
 12. A composition according to any one of the preceding claimswherein the treat level of the friction reducing additive is from 1-500mg per kg of gasoline.
 13. A composition according to any one of thepreceding claims wherein the treat level of the friction reducingadditive is from 4-200 ppm based on the gasoline.
 14. A compositionaccording to any one of the preceding claims wherein the treat level ofthe friction reducing additive is from 10-100 ppm based on the gasoline.15. A composition according to any one of the preceding claims whereinthe treat level of the friction reducing additive is from 25-75 ppmbased on the gasoline.